---
description: Write integration tests for Cloudflare Workers with the createTestHarness API in Wrangler.
title: Integration test harness
image: https://developers.cloudflare.com/og-docs.png
---

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> Documentation Index  
> Fetch the complete documentation index at: https://developers.cloudflare.com/workers/llms.txt  
> Use this file to discover all available pages before exploring further.

# Integration test harness

Last updated Aug 24, 2026|Copy as Markdown|[View as Markdown](https://mchen-ai-models-sync.previews.developers.cloudflare.com/workers/testing/test-harness/index.md)|[Agent setup](https://mchen-ai-models-sync.previews.developers.cloudflare.com/agent-setup/)

[createTestHarness()](https://mchen-ai-models-sync.previews.developers.cloudflare.com/workers/wrangler/api/#createtestharness) is a Wrangler API for integration testing from any Node.js test runner. It runs one or more Workers from [Wrangler](https://mchen-ai-models-sync.previews.developers.cloudflare.com/workers/wrangler/) projects or Vite projects that use the [Cloudflare Vite plugin](https://mchen-ai-models-sync.previews.developers.cloudflare.com/workers/vite-plugin/).

[Get started](https://mchen-ai-models-sync.previews.developers.cloudflare.com/workers/testing/test-harness/get-started/)[View complete example](https://github.com/cloudflare/workers-sdk/tree/main/fixtures/create-test-harness-example) 

## Features

* Runs production build output from Wrangler or the Cloudflare Vite plugin
* Dispatches requests and events to one or more Workers
* Provides access to bindings and local storage from tests
* Captures logs and diagnostic output from the Workers runtime

## Guides

### [Configure the test harness](https://mchen-ai-models-sync.previews.developers.cloudflare.com/workers/testing/test-harness/configure/)

Configure Workers, test values, lifecycle hooks, and failure diagnostics.

### [Prepare test state](https://mchen-ai-models-sync.previews.developers.cloudflare.com/workers/testing/test-harness/prepare-test-state/)

Seed storage, mock outbound requests, and replace bindings.

### [Interact with Workers](https://mchen-ai-models-sync.previews.developers.cloudflare.com/workers/testing/test-harness/interact-with-workers/)

Test routes, dispatch events, control Workflows, and assert logs.

### [Integrations](https://mchen-ai-models-sync.previews.developers.cloudflare.com/workers/testing/test-harness/integrations/)

Use the test harness with MSW and Playwright.

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## On this page

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